Explanation of programming distributions in phase-change memory arrays based on crystallization time statistics

In order to validate phase change memory (PCM) technology, the programming reliability, in terms of reading window between the programmed and erased state, must be guaranteed at array level with an error less then 1 part-per-billion. The reset distribution is significantly influenced by the quenching operation [Mantegazza D, Ielmini D, Pirovano A, Gleixner B, Lacaita A L, Varesi E, et al. Electrical characterization of anomalous cells in phase change memory arrays. IEDM Tech Dig 2006:53-56]. In this paper this phenomenon is explained in terms of PCM active material crystallization statistics. A significant spread in the crystallization times among PCM cells is detected both in the write-reset operation from the melted-amorphous state (quenching) and in the erase-set operation from the solid-amorphous state. At statistical level, a correlation between set at high and low temperatures and quenching behavior of cells is found, allowing to describe the programming distributions uniquely in terms of crystallization times statistics.